Electromechanical shifting systems are used to transmit the adjusting movement of a gearshift lever to a corresponding shift position of a transmission. Instead of the classical transmission of the gearshift lever position via cables and gear shift linkages to the transmission, a sensor system is used, which detects the particular current position of the gearshift lever from the cooperation of actuators and sensors. The identity of the gearshift lever position detected is transmitted to a control unit of the transmission with electric, electronic, electro-optic or other similar means and converted by the control unit into a corresponding shifting state of the transmission. Such shifting systems are currently known under the name shift-by-wire. They are used preferably in automated manual transmissions or automatic transmissions. Automated manual transmissions can be manufactured at a lower cost and as lighter and more compact units compared with automatic transmissions. As a result and especially in connection with the high efficiency due to the system, great significance is attached to the automated manual transmission in the future development of motor vehicles.
The position of the gearshift lever is frequently detected in electromechanical shifting systems with magnetically or optically acting sensors, e.g., Hall sensors, optoreflex sensors or the like. During the movement of the gearshift lever, distinction is made between two movement spaces, which correspond to the pivoting directions of the gearshift lever about two pivot axes. The “selection” movement space preferably comprises a change in the gearshift lever position in a first direction, and the “shifting” movement space a change in the gearshift lever position at right angles to this direction. In case of orthogonal movement spaces, the two pivot axes are also arranged at right angles to one another, and the first direction may correspond, e.g., to the direction of the vehicle. However, it is also possible for the first direction to extend at right angles to the direction of the vehicle. The position of a gearshift lever is correspondingly detected separately for the two movement spaces. The shifting of the transmission selected with a certain position of the gearshift lever is obtained from the combination of the projections of this position to the “selection” and “shifting” movement spaces.
To keep the manufacturing effort needed for an electromechanical gearshift lever module low, the sensors for the “selection” and “shifting” movement spaces are accommodated on a single planar, i.e., flat and noncurved printed circuit board. The actuator is mechanically connected with the gearshift lever and is arranged opposite the printed circuit board with the sensors. Since a change in the gearshift lever position takes place due to the pivoting of the gearshift lever, the clearance between the actuator and a sensor changes with the shift position of the gearshift lever in this design.
The range of action of the actuators is, in general, limited very narrowly, so that the sensors are responded to differently. If, for example, a magnetic sensor system with a permanent magnet as the actuator is used, the activating magnetic field has a gaussian distribution of the magnetic field contour. The width and the intensity of the distribution change with the distance from the magnet. The switch-on and switch-off thresholds of the magnetic field-sensitive sensors, for example, Hall sensors, are therefore different for each shift position.
To counteract this effect, a printed circuit board may be curved such that the distances between the actuator and the respective sensors are kept constant in the different shifting states. However, the manufacture of a correspondingly curved printed circuit board is associated with great effort and therefore high manufacturing costs. As an alternative, a sensor may be designed individually for each shift position. However, this solution also leads to considerable extra costs in manufacture.
A flat sensor system can be embodied by means of a slide system carried by the gearshift lever. This solution is very complicated in terms of design and has the drawback that the tolerance chain in the detection of the gearshift lever position is made longer, besides the extra costs caused by this solution in the manufacture.
A technically good solution is offered by the arrangement of two planar printed circuit boards at right angles to one another. Each of the noncurved printed circuit boards carries here a flat sensor system for only one of the “selection” and “shifting” movement spaces, so that the distances between the actuators and the respective sensors do not change for the different positions of the gearshift lever. Since each shift position is composed of a “selection” position combined with a “shifting” position, considerably more sensors are also necessary between two actuators in this solution than in a solution corresponding to the above-mentioned solution designs. Furthermore, the terminals of the two boards must be combined, so that the embodiment of this solution is extremely complicated and cost-intensive.